Chinese naval vessels and military aircraft encircled Taiwan on Thursday in a drill Beijing dubbed a "strong punishment" for the self-ruled island.
The exercise comes days after Taipei swore in its new leader, Lai Ching-te, who vowed to defend democracy.
China's military described the latest show of force as a "strong punishment for the separatist acts of 'Taiwan independence' forces".
The drills involve aircraft and ships surrounding the island to test their combat capabilities, according to the People's Liberation Army (PLA).
The Taiwanese Military of National Defence held a press conference where Major General Huang Wenqi announced that a total of 31 Chinese naval forces had been detected, including 15 combat ships and 16 coast guard ships. Additionally, 28 aircraft entered the response area.
Taiwan responded by deploying air, ground, and sea forces, with the island's defence ministry vowing to "defend freedom".
A Taipei spokesperson condemned China's "provocative military behaviour".
Taiwan's new leader, Lai, said: "In face of the many threats and attempts of infiltration from China, we must demonstrate our resolution to defend our nation," hailing a "glorious" era of democracy.
China warned of strong reprisals to Lai's speech, branding him a "dangerous separatist".
The drills, which began at 7.45am local time, are taking place in the Taiwan Strait and to the north, south and east of the island, said PLA Eastern Theater Command Naval Colonel Li Xi.
State broadcaster CCTV declared the "Joint Sword-2024A" drills "a powerful disciplinary action" against Taiwanese separatism.
China's military released posters touting its "cross-strait lethality" featuring rockets, jets, and naval vessels next to blood-stained text declaring, "The weapon aimed at 'Taiwan independence' to kill 'independence' is already in place."
Taiwan's Kaohsiung port and cut off energy imports and support from US allies.
Similar drills were announced in August last year after Lai, then vice president, stopped over in the United States on his way to Paraguay.
These followed April drills simulating the island's encirclement after Lai's predecessor, Tsai Ing-wen, met then-US House Speaker Kevin McCarthy.
Major military exercises were also launched in 2022 after Nancy Pelosi, then the US House Speaker, visited Taiwan.
The Taiwan Strait is one of the world's most important maritime trade routes, and Taiwan is a key tech manufacturer, particularly of semiconductors.
The United States, Taiwan's most important ally, switched its diplomatic recognition from Taiwan to China in 1979 but continues to supply military hardware to the island.
President Joe Biden has said he does not support Taiwan's independence but would back sending forces to defend it, maintaining a policy of strategic ambiguity.
US Lieutenant General Stephen Sklenka, speaking in Canberra, described the exercises as "concerning" but not unexpected. The United States did not give an immediate official response to the drills.
